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Some roadways, which do not behave as "wholly rough pipe" as we expected, will have different impact on airflow in a mine ventilation network because of the low Reynolds numbers. For a "non-Wholly-rough" roadway, its resistance factor (R) or the friction factor (¦) is not only dependent upon the relative roughness but also dependent upon the Reynolds number, which varies directly as the flow rate. In this case, R or ¦ is no longer a constant independent of flow rate. Thus, in order to correctly calculate the friction drag of the same roadway for different flow rates, ¦ must be correctly calculated firstly by an appropriate method. After introducing the concept of Equivalent Roughness of mine roadway, the Colebrook formula can serve as this method. Known from the conventional method for calculating the friction drag of mine roadway, the method introduced in this paper is called the Equivalent Roughness Method (ERM). By using the ERM to analyze the airflow direction of the diagonal airway in a simple diagonal network, a new calculating example is presented.

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Jun 11th, 12:00 AMJun 17th, 12:00 AM

Equivalent Roughness and Its Application in Calculating Friction Drag of Mine Roadway

Rolla, MO

Some roadways, which do not behave as "wholly rough pipe" as we expected, will have different impact on airflow in a mine ventilation network because of the low Reynolds numbers. For a "non-Wholly-rough" roadway, its resistance factor (R) or the friction factor (¦) is not only dependent upon the relative roughness but also dependent upon the Reynolds number, which varies directly as the flow rate. In this case, R or ¦ is no longer a constant independent of flow rate. Thus, in order to correctly calculate the friction drag of the same roadway for different flow rates, ¦ must be correctly calculated firstly by an appropriate method. After introducing the concept of Equivalent Roughness of mine roadway, the Colebrook formula can serve as this method. Known from the conventional method for calculating the friction drag of mine roadway, the method introduced in this paper is called the Equivalent Roughness Method (ERM). By using the ERM to analyze the airflow direction of the diagonal airway in a simple diagonal network, a new calculating example is presented.